title: Tobacco and cannabis co-occurrence: does route of administration matter?
abstract: BACKGROUND
  Qualitative research suggests that a shared route of administration (i.e. via inhalation) for the common forms of both tobacco (i.e. cigarettes) and cannabis (i.e. joints) may contribute to their co-occurring use.
  
  
  METHODS
  We used data on 43,093 U.S. adults who participated in the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) to examine whether cannabis use and abuse/dependence were associated with smoked (cigarettes, cigars, pipes) versus smokeless (snuff, chewed tobacco) forms of tobacco use, even after controlling for socio-demographic, psychiatric and substance-related covariates.
  
  
  RESULTS
  Tobacco smoking was associated with a 3.3-4.5 times increased risk for cannabis use and abuse/dependence respectively. After covariate adjustment, importantly for nicotine dependence, smoking tobacco (but not smokeless tobacco) was still significantly associated with both cannabis use (multinomial odds-ratio (MOR) 1.99) and cannabis dependence (MOR 1.55). In contrast, use of smokeless tobacco was not significantly correlated with elevated rates of cannabis use (MOR 0.96) or abuse/dependence (MOR 1.04).
  
  
  CONCLUSIONS
  Route of administration may play an important role in the observed association between tobacco and cannabis use. This may represent a physiological adaptation of the aero-respiratory system and/or index social and cultural influences surrounding the use of smoked versus smokeless forms of tobacco.
authors.affiliation: Washington University School of Medicine, Department of Psychiatry, 660 S. Euclid, CB 8134, St. Louis, MO 63110, United States. arpana@wustl.edu
authors.forename: Arpana
authors.initials: A
authors.lastname: Agrawal
authors.forename: Michael T
authors.initials: MT
authors.lastname: Lynskey
mesh_terms: D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D002189:Marijuana Abuse / Q000150:complications* / Q000453:epidemiology*; D008385:Marijuana Smoking / Q000453:epidemiology*; D001523:Mental Disorders / Q000523:psychology; D008875:Middle Aged; D016017:Odds Ratio; D011569:Psychiatric Status Rating Scales; D012907:Smoking / Q000453:epidemiology*; D012959:Socioeconomic Factors; D014029:Tobacco Use Disorder / Q000150:complications* / Q000453:epidemiology*; D014030:Tobacco, Smokeless; D014481:United States / Q000453:epidemiology; D055815:Young Adult